An optical encoder is widely used in various environments to determine the movement or position of an object with respect to an arbitrary criterion.
An optical sensor and an encoder pattern are used in a general optical encoder. The optical sensor is focused on a surface of the encoder pattern. When the optical sensor moves on the basis of the encoder pattern or the encoder pattern moves on the basis of the optical sensor, the optical sensor passes through the encoder pattern or deciphers an optical pattern reflected from the encoder pattern, thereby detecting the movement or position.
Recently, demand for an accurate encoder having high resolution has been increasing in industrial fields where extremely sensitive operations are required, like in the robotics industry.
Korean Patent Laid-Open Publication No. 2007-0026137 provides an optical encoder capable of detecting an index channel even without an element for detecting an index which becomes a standard upon determining a position. However, Korean Patent Laid-Open Publication No. 2007-0026137 does not disclose a way to measure a rotational angle using high resolution.